It’s really hard what to suggest.
Absolutely tell him you do not want to be a one income household. A sahp set up only ever works if both people want it. If you don’t, tell him that and if he doesn’t accept it you may as well split now as you can not force him to not hand his notice in.
It’s also difficult to say about the division of labour. It is true a female teacher posting that she worked part time, would get sympathy from MN if the male partner was telling them they don’t do enough housework or admin. Especially, when one child is only one. Teachers often work more than their official hours.
Also, it’s really not unusual when a marriage is going down the drain for the working partner to decide they are being taken advantage of and the sahp does nothing. Men the world over have said this about their sahm wives during divorce. I can’t see why it would be any different the other way round. When marriages are in the final stages, both sides often feel badly done to and claim the other never does enough.
He could be not doing enough. Op could be just feeling badly done to and so (subconsciously) framing her life as worse than his. No one here knows.
And it is entirely natural that he would stand more of a chance of having the kids more if they split. That’s why women, get majority custody more often than men. Because they have been the main care giver before the split. Admin and cleaning doesn’t usually come into it.
As for the ‘why doesn’t anyone warn men they will see their kids less if their wife is a sahp and they split’, since MN is mainly frequented by women we can’t answer that. Why not go ask men why they don’t point that out when their friends, or people posting on advice forums mention it? Why would it be MNs or women’s responsibility to make sure men know the really obvious consequences of decisions they make?
I mean it could be that a lot of time, men (usually) simply aren’t fussed about having the majority custody. Or they do know but think the benefits outweigh the risks. It’s still not women’s jobs to make sure men know what will happen if their marriage splits.
It’s not even women’s jobs to tell other women. And we don’t, unless someone is specifically asking for advice. Like the female op here is.
If you think men need more education in this area. Work with men to provide it.